Generally a fluorescent indicator panel used as a digital indicator for expressing characters or symbols in a digital form in electronic meters and calculators has the constitution as illustrated in FIG. 1.
Wiring layers 12 such as connection terminal pattern 12a and an inner connection pattern 12b, an insulative layer 13, and a conductive layer 14 forming a anode segment of a required pattern are sequentially deposited upon an insulative base board 11 through a printing method and the like, thus the base board 11 constituting a printed board.
Meanwhile, the base board 11 is usually made of a ceramic material or a glass material, and therefore, the wiring layer 12, the insulative layer 13 and the conductive layer 14 which are printed on the base board 11 are first coated with a paint or paste containing silicic acid ingredient such as kasil (K.sub.2 SiO.sub.3) or crystalline glass powder (to be called hereinafter "frit"), thereafter the layers 12,13,14 being baked so as for them to be united with the base board 11.
A fluorescent material is spread on the conductive layer 14 of the printed board formed by the above described method, thereby forming a fluorescent layer 15. Above the fluorescent layer 15, a metal component, i.e. a grid 16 or a support (not shown) for supporting a filament 17 is disposed, and then, an envelope 18 is attached sealingly to the printed board for covering all of the above described components, thereby completing the manufacturing of a fluorescent indicator panel.
In the conventional manufacturing method of the fluorescent indicator panel described above, the metal component such as a grid 16 or a support for supporting the filament 17 is, for example, attached to the printed board by securing the related parts by means of the frit which is cited as a prior art in Japanese Utility Model Publication No. Sho 56-20932.
However, the above mentioned frit F essentially requires a high temperature baking under 450.degree..about.500.degree. C. in order to crystallize it, and therefore, there arises the problem that a baking process has to be added in attaching the grid 16. Further, the organic binder and the like contained in the frit F can be decomposed at the high temperature to generate harmful gases, and these gases are absorbed into the already formed fluorescent layer 15, thereby deteriorating the luminance of the fluorescent layer 15. Particularly, if the red fluorescent material which is low in the thermal stability is subjected to heating up to the baking temperature, the luminance is drastically lowered, thereby making it difficult to use it in the fluorescent indicator panel.
Further, until the crystallization is achieved after the baking process, the semi-fluidal frit supports the metal components such as the grid 16, and therefore, its exact positioning is very difficult, with the result that the precision of the fluorescent indicator panel is lowered. Further, the baking process which is carried out at the time of attaching the metal components in order to maintain the precision is much more fastidious compared with the baking process which is carried out at the time of forming the printed board, and therefore, the product rejection rate is increased, thereby aggravating the productivity.
Further, the above mentioned baking process is carried out under an oxidizing atmosphere, and therefore, there is accompanied the problem that the grid 16 is oxidized, and its efficiency is lowered.